The Internal Revenue Service is looking for 4,781 Southern California taxpayers who are due to receive a combined $5 million in undeliverable tax refunds. These are refund checks that were returned to the IRS by the U.S. Postal Service due to mailing address errors.

Nationally, IRS is looking for 107,831 taxpayers who are owed a combined $124 million. In addition, more than 15,000 California taxpayers are owed $16.6 million, or about 13% of the total.

All a taxpayer has to do is update his or her address once. Some taxpayers are due more than one check.

"We are eager to get this money into the hands of taxpayers, so don't delay if you think you are missing a refund," said IRS Commissioner Doug Shulman. "The sooner you update your address information, the quicker you can get your refund."

The vast majority of checks mailed out by the IRS each year reach their rightful owner. Only a very small percent are returned by the U.S. Postal Service as undeliverable.